Conventionally, various electronic devices are mounted on a vehicle or the like, and a wiring harness (electric wire) is arranged therein for transmitting electric power, a control signal, and the like. Further, in recent years, a vehicle running with a driving force of a motor driven by electric power of a battery such as a hybrid vehicle or an electric vehicle becomes common. In such a battery-driven vehicle, DC current outputted from the battery is converted into AC current of a specific frequency by an inverter, and a motor is driven by this AC current. As a power line which transmits DC current by connecting the battery with the inverter in this way, two-core wire corresponding to two positive and negative electrodes is used (for example, see PTL 1).
The electric wire (cable) described in PTL 1 includes: two insulated core wires made by conductors such as single wire or twisted wire covered by an insulator; an inclusion provided around these insulated core wires; a suppressing wound tape wound around the two insulated core wires and the inclusion; and a sheath covering an outer periphery of the suppressing wound tape. This electric wire can be light-weighted and environmentally friendly by properly selecting components of the inclusion. However, the electric wire, in which two insulated core wires are arranged in parallel like this electric wire, is easy to be bent in a direction of which bending axis is an arranging direction of the two insulated core wires, but is difficult to be bent in a direction of which bending axis is perpendicular to the arranging direction among two directions perpendicular to an extending direction of the electric wire. Therefore, because flexibility (non-flexibility) of the electric wire is directional (anisotropic), inconvenience is generated such that a wiring path is regulated and a wiring distance (wire length) becomes long when the electric wire is arranged in a vehicle or the like, because the electric wire cannot be bent freely. Further, a diameter of the sheath is more than twice a diameter of the insulated core wire, and a useless space is generated in the sheath. Thereby, the diameter of the sheath becomes larger, and a large space is necessary for wiring.
In contrast, as an electric wire, the electric wire (coaxial wire) made by coaxially and sequentially laminating a center conductor, an insulator coveting an outer periphery of the center conductor, an outer conductor covering an outer periphery of the insulator, and an outer cover covering an outer periphery of the outer conductor is used. Because the coaxial wire is isotropic, wiring flexibility can be improved, and a wiring space can be reduced by shrinking an outer diameter of the electric wire. As a method for manufacturing a coaxial wire, it is proposed that the method includes the steps of: producing a center conductor from the stranded wire; forming an insulator around the center conductor by extruding molten resin; providing an outer conductor composed of such as twisted wire, helical stranded wire, or metal tape around this insulator; and forming an outer cover around this outer conductor by extruding molten resin (for example, see PTL 2).